U.S. patent application number 12/544336 was filed with the patent office on 2010-02-25 for semiconductor device and amplification device generating triangular wave synchronized with clock signal.
This patent application is currently assigned to Rohm Co., Ltd.. Invention is credited to Kuniyuki Kubo, Koji Saito.
Application Number | 20100045350 12/544336 |
Document ID | / |
Family ID | 41695785 |
Filed Date | 2010-02-25 |
United States Patent
Application |
20100045350 |
Kind Code |
A1 |
Saito; Koji ; et
al. |
February 25, 2010 |
Semiconductor Device and Amplification Device Generating Triangular
Wave Synchronized with Clock Signal
Abstract
A semiconductor device includes a current control circuit for
outputting and sinking a current in synchronization with a received
clock signal; and a current/voltage conversion circuit having a
first capacitor charged and discharged by the current control
circuit outputting and sinking the current, respectively, and
outputting a triangular wave based on the charge stored in the
first capacitor.
Inventors: |
Saito; Koji; (Kyoto-shi,
JP) ; Kubo; Kuniyuki; (Kyoto-shi, JP) |
Correspondence
Address: |
FISH & RICHARDSON P.C.
P.O. BOX 1022
MINNEAPOLIS
MN
55440-1022
US
|
Assignee: |
Rohm Co., Ltd.
Kyoto
JP
|
Family ID: |
41695785 |
Appl. No.: |
12/544336 |
Filed: |
August 20, 2009 |
Current U.S.
Class: |
327/132 ;
327/136; 327/137 |
Current CPC
Class: |
H03K 7/08 20130101; H03F
3/217 20130101; H03K 4/90 20130101; H03K 4/06 20130101 |
Class at
Publication: |
327/132 ;
327/136; 327/137 |
International
Class: |
H03K 4/06 20060101
H03K004/06; H03K 4/90 20060101 H03K004/90 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 20, 2008 |
JP |
2008-211716 |
Claims
1. A semiconductor device comprising: a current control circuit for
outputting and sinking a current in synchronization with a received
clock signal; and a current/voltage conversion circuit having a
first capacitor charged and discharged by said current control
circuit outputting and sinking the current, respectively, and
outputting a triangular wave based on a charge stored in said first
capacitor.
2. The semiconductor device according to claim 1, wherein said
current/voltage conversion circuit includes a first differential
amplifier having a first input terminal coupled to said current
control circuit and a first end of said first capacitor, a second
input terminal receiving a first reference voltage and an output
terminal coupled to a second end of said first capacitor, and a
first resistor connected between said current control circuit and a
coupling point between the first input terminal of said first
differential amplifier and the first end of said first
capacitor.
3. The semiconductor device according to claim 2, further
comprising: a second differential amplifier having a first input
terminal coupled to the output terminal of said first differential
amplifier, a second input terminal receiving a second reference
voltage and an output terminal; a second capacitor connected
between the first input terminal of said second differential
amplifier and the output terminal of said second differential
amplifier; and a second resistor connected between a coupling point
between one end of said second capacitor and the first input
terminal of said second differential amplifier, and a coupling
point between the second end of said first capacitor and the output
terminal of said first differential amplifier, wherein said first
reference voltage is output from the output terminal of said second
differential amplifier.
4. The semiconductor device according to claim 2, wherein a
resistance value of said first resistor is variable.
5. The semiconductor device according to claim 1, further
comprising a comparison circuit for comparing said triangular wave
with a second reference voltage, wherein said current/voltage
conversion circuit changes a direct current level of the triangular
wave based on a comparison result by said comparison circuit.
6. The semiconductor device according to claim 1, wherein said
current control circuit includes a first transistor of a first
conduction type having a control electrode receiving said clock
signal, a first conductive electrode coupled to a node supplied
with a power supply voltage and a second conductive electrode
coupled to said first capacitor, and a second transistor of a
second conduction type having a control electrode receiving said
clock signal, a first conductive electrode coupled to a node
supplied with a ground voltage and a second conductive electrode
coupled to said first capacitor.
7. An amplification device comprising: a D/A converter for
converting a digital signal into an analog signal; an integration
circuit for integrating and outputting said converted analog
signal; a triangular wave generating circuit for generating a
triangular wave; a comparator for comparing said integrated analog
signal with said triangular wave and outputting a signal
representing a comparison result; and a first current control
circuit for outputting a current based on the signal received from
said comparator, and said triangular wave generating circuit
including a second current control circuit for outputting and
sinking a current in synchronization with a received clock signal,
and a current/voltage conversion circuit having a first capacitor
charged and discharged by said second current control circuit
outputting and sinking the current, respectively, and outputting
said triangular wave based on a charge stored in said first
capacitor.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a semiconductor device and
an amplification device, and particularly to a semiconductor device
and an amplification device generating a triangular wave
synchronized with a clock signal.
[0003] 2. Description of the Background Art
[0004] The so-called class D amplifier for amplifying power using a
switching circuit is known. The class D amplifier includes, for
example, an integrator, a triangular wave generating circuit, a
comparator comparing an output of the integrator with an output of
the triangular wave generating circuit, and a current control
circuit for outputting a current based on the signal received from
the comparator. The output of the comparator is fed back to the
input of the integrator.
[0005] As an example of the triangular wave generating circuit,
"Design and Fabrication of Class D/Digital Amplifier" (pp. 60-61)
authored by Jun Honda and issued by CQ Publishing Co., Ltd. on 2004
(Non-Patent Document 1), for example, discloses a configuration in
which a triangular wave generating circuit includes a differential
amplifier, an integration circuit configured of a resistor and a
capacitor, and a comparator having hysteresis.
[0006] Furthermore, as an example of the triangular wave generating
circuit in the class D amplifier, Japanese Patent Laying-Open No.
2006-020177 (Patent Document 1), for example, discloses a
configuration in which a triangular wave generating circuit used in
the class D amplifier provided with a switching amplification stage
for performing switching amplification of the pulse-width
modulation output obtained by performing pulse-width modulation of
the input signal includes first constant current means for
outputting a first constant current proportional to the positive
power supply voltage of the switching amplification stage, second
constant current means for outputting a second constant current
proportional to the negative power supply voltage of the switching
amplification stage, constant current selection means for
periodically and alternately selecting the first and second
constant currents with a high impedance element, first integration
means for outputting an integrated output as a triangular wave, the
first integration means having a capacity charged with the selected
constant current interposed between the input terminal and the
output terminal of the amplifier, and second integration means for
integrating the output of the first integration means and
negatively feeding back the integrated output to the input terminal
of the first integration means as a phase correction instruction
for the triangular wave.
[0007] However, in the case where the triangular wave generating
circuit disclosed in each of Non-Patent Document 1 and Patent
Document 1 is used along with a digital circuit, the interference
of a system clock and the like produces beat noise, which may lead
to deterioration of the performance.
SUMMARY OF THE INVENTION
[0008] An object of the present invention is to provide a
semiconductor device and an amplification device which are capable
of generating a triangular wave and preventing performance
deterioration caused by interference of a system clock and the
like.
[0009] The semiconductor device according to an aspect of the
present invention includes a current control circuit for outputting
and sinking a current in synchronization with a received clock
signal; and a current/voltage conversion circuit having a first
capacitor charged and discharged by the current control circuit
outputting and sinking the current, respectively, and outputting a
triangular wave based on a charge stored in the first
capacitor.
[0010] Preferably, the current/voltage conversion circuit includes
a first differential amplifier having a first input terminal
coupled to the current control circuit and a first end of the first
capacitor, a second input terminal receiving a first reference
voltage and an output terminal coupled to a second end of the first
capacitor; and a first resistor connected between the current
control circuit and a coupling point between the first input
terminal of the first differential amplifier and the first end of
the first capacitor.
[0011] More preferably, the semiconductor device further includes a
second differential amplifier having a first input terminal coupled
to the output terminal of the first differential amplifier, a
second input terminal receiving a second reference voltage and an
output terminal; a second capacitor connected between the first
input terminal of the second differential amplifier and the output
terminal of the second differential amplifier; and a second
resistor connected between a coupling point between one end of the
second capacitor and the first input terminal of the second
differential amplifier, and a coupling point between the second end
of the first capacitor and the output terminal of the first
differential amplifier. The first reference voltage is output from
the output terminal of the second differential amplifier.
[0012] More preferably, a resistance value of the first resistor is
variable.
[0013] Preferably, the semiconductor device further includes a
comparison circuit for comparing the triangular wave with a second
reference voltage, and the current/voltage conversion circuit
changes a direct current level of the triangular wave based on a
comparison result by the comparison circuit.
[0014] Preferably, the current control circuit includes a first
transistor of a first conduction type having a control electrode
receiving the clock signal, a first conductive electrode coupled to
a node supplied with a power supply voltage and a second conductive
electrode coupled to the first capacitor; and a second transistor
of a second conduction type having a control electrode receiving
the clock signal, a first conductive electrode coupled to a node
supplied with a ground voltage and a second conductive electrode
coupled to the first capacitor.
[0015] Furthermore, an amplification device according to an aspect
of the present invention includes a D/A (Digital-to-Analog)
converter for converting a digital signal into an analog signal; an
integration circuit for integrating and outputting the converted
analog signal; a triangular wave generating circuit for generating
a triangular wave; a comparator for comparing the integrated analog
signal with the triangular wave and outputting a signal
representing a comparison result; and a first current control
circuit for outputting a current based on the signal received from
the comparator. The triangular wave generating circuit includes a
second current control circuit for outputting and sinking a current
in synchronization with a received clock signal; and a
current/voltage conversion circuit having a first capacitor charged
and discharged by the second current control circuit outputting and
sinking the current, respectively, and outputting the triangular
wave based on a charge stored in the first capacitor.
[0016] According to the present invention, a triangular wave can be
generated to thereby prevent performance deterioration caused by
interference of a system clock and the like.
[0017] The foregoing and other objects, features, aspects and
advantages of the present invention will become more apparent from
the following detailed description of the present invention when
taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a diagram of the configuration of a motor system
according to a first embodiment of the present invention.
[0019] FIG. 2 is a diagram of the configuration of a triangular
wave generating circuit according to the first embodiment of the
present invention.
[0020] FIG. 3 is a waveform diagram showing the operation of the
triangular wave generating circuit according to the first
embodiment of the present invention.
[0021] FIG. 4 is a diagram of the configuration of a triangular
wave generating circuit according to a second embodiment of the
present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] The embodiments of the present invention will be hereinafter
described with reference to the accompanying drawings, in which the
same or corresponding components are designated by the same
reference characters, and description thereof will not be
repeated.
First Embodiment
[0023] FIG. 1 is a diagram of the configuration of a motor system
according to a first embodiment of the present invention.
[0024] Referring to FIG. 1, a motor system 301 includes an
oscillator OSC, a microstep circuit 1, a D/A (Digital-to-Analog)
converter (DAC) 2, an amplification device 201, and a motor M.
Amplification device 201 includes an arithmetic unit 3, an
integrator 4, a comparator 5, a current control circuit 6, and a
triangular wave generating circuit 101.
[0025] Microstep circuit 1 calculates a drive current value used
for microstep-driving motor M based on the oscillation signal
received from oscillator OSC, and outputs the drive data showing
this drive current value to D/A converter 2.
[0026] D/A converter 2 converts the drive data received from
microstep circuit 1 into an analog signal, and outputs the signal
to amplification device 201.
[0027] Amplification device 201 amplifies the analog signal
received from D/A converter 2 to generate a drive current IDRV, and
supplies the current to motor M. Amplification device 201 is
included in one integrated circuit having, for example, external
terminals T1 and T2.
[0028] More specifically, arithmetic unit 3 adds the analog signal
received from D/A converter 2 via external terminal T1 and the
signal fed back from current control circuit 6, and outputs the
result to integrator 4.
[0029] Integrator 4 integrates the analog signal received from
arithmetic unit 3 and outputs the result to comparator 5.
Triangular wave generating circuit 101 generates and outputs a
triangular wave TRWOUT to comparator 5.
[0030] Comparator 5 compares the analog signal received from
integrator 4 with triangular wave TRWOUT received from triangular
wave generating circuit 101, and outputs the signal representing
the comparison result.
[0031] Current control circuit 6 outputs drive current IDRV based
on the signal received from comparator 5. Drive current IDRV is
supplied to motor M via external terminal T2.
[0032] FIG. 2 is a diagram of the configuration of the triangular
wave generating circuit according to the first embodiment of the
present invention.
[0033] Referring to FIG. 2, triangular wave generating circuit 101
includes a current control circuit 51 and a current/voltage
conversion circuit 52.
[0034] Current control circuit 51 includes a P-channel MOS (Metal
Oxide Semiconductor) transistor M1 and an N-channel MOS transistor
M2. Current/voltage conversion circuit 52 includes a differential
amplifier G1, a capacitor C1 and a resistor R1.
[0035] P-channel MOS transistor M1 includes a gate receiving a
reference clock REFCLK, a source coupled to a node VDD supplied
with a power supply voltage, and a drain coupled to capacitor C1.
N-channel MOS transistor M2 includes a gate receiving reference
clock REFCLK, a source coupled to a node VSS supplied with a ground
voltage, and a drain coupled to capacitor C1.
[0036] Differential amplifier G1 has an inversion input terminal
coupled to current control circuit 51 and the first end of
capacitor C1, a non-inversion input terminal receiving a reference
voltage VREF1, and an output terminal coupled to the second end of
capacitor C1. Resistor R1 is connected between the node connecting
a drain of P-channel MOS transistor M1 and a drain of N-channel MOS
transistor M2, and the node connecting the inversion input terminal
of differential amplifier G1 and the first end of capacitor C1.
[0037] Current control circuit 51 outputs and sinks a current in
synchronization with reference clock REFCLK.
[0038] Current/voltage conversion circuit 52 serving as an
integrator includes capacitor C1 charged and discharged by current
control circuit 51 outputting and sinking the current,
respectively, and outputs triangular wave TRWOUT based on the
charge stored in capacitor C1.
[0039] FIG. 3 is a waveform diagram showing the operation of the
triangular wave generating circuit according to the first
embodiment of the present invention.
[0040] Referring to FIG. 3, when reference clock REFCLK transitions
from a logic high level to a logic low level, the current flows
from node VDD through N-channel MOS transistor M1 into
current/voltage conversion circuit 52. Consequently, capacitor C1
is charged and the level of output voltage TRWOUT is lowered.
Furthermore, when reference clock REFCLK transitions from a logic
low level to a logic high level, capacitor C1 is discharged and the
current flows from current/voltage conversion circuit 52 through
N-channel MOS transistor M2 into node VSS. This raises the level of
output voltage TRWOUT.
[0041] In other words, the level and cycle of triangular wave
TRWOUT can be controlled by controlling the frequency of reference
clock REFCLK.
[0042] In the case where the frequency of reference clock REFCLK is
lowered, triangular wave TRWOUT may increase in amplitude to cause
distortion. However, in the triangular wave generating circuit
according to the first embodiment of the present invention, the
resistance value of resistor R1 is variable. This allows the
amplitude of triangular wave TRWOUT to be adjusted. For example,
since the amplitude of triangular wave TRWOUT can be reduced by
increasing the resistance value of resistor R1, distortion of
triangular wave TRWOUT can be prevented.
[0043] In the case where the triangular wave generating circuit
disclosed in each of Non-Patent Document 1 and Patent Document 1 is
used along with a digital circuit, the interference of a system
clock and the like causes beat noise, which may lead to
deterioration of the performance.
[0044] However, in the triangular wave generating circuit according
to the first embodiment of the present invention, current control
circuit 51 outputs and sinks a current in synchronization with
reference clock REFCLK. Current/voltage conversion circuit 52
includes capacitor C1 charged and discharged by current control
circuit 51 outputting and sinking the current, respectively, and
outputs triangular wave TRWOUT based on the charge stored in
capacitor C1. According to this configuration, triangular wave
TRWOUT synchronized with reference clock REFCLK can be generated.
Therefore, in the triangular wave generating circuit according to
the first embodiment of the present invention, beat noise occurring
due to interference of a system clock and the like can be
prevented, and thus, performance deterioration can be
prevented.
[0045] Another embodiment of the present invention will be
hereinafter described with reference to the accompanying drawings,
in which the same or corresponding components are designated by the
same reference characters, and description thereof will not be
repeated.
Second Embodiment
[0046] The present embodiment relates to a triangular wave
generating circuit additionally provided with a function of
adjusting the level of the triangular wave as compared with the
triangular wave generating circuit according to the first
embodiment. The triangular wave generating circuit according to the
present embodiment is the same as that according to the first
embodiment except for features as described below.
[0047] FIG. 4 is a diagram of the configuration of a triangular
wave generating circuit according to the second embodiment of the
present invention.
[0048] Referring to FIG. 4, a triangular wave generating circuit
102 includes a current control circuit 51, a current/voltage
conversion circuit 52, and a comparison circuit 53.
[0049] Current control circuit 51 includes a P-channel MOS
transistor M1 and an N-channel MOS transistor M2. Current/voltage
conversion circuit 52 includes a differential amplifier G1, a
capacitor C1 and a resistor R1. Comparison circuit 53 includes a
differential amplifier G2, a resistor R2 and a capacitor C2.
[0050] Differential amplifier G1 has an inversion input terminal
coupled to current control circuit 51 and the first end of
capacitor C1, a non-inversion input terminal receiving a reference
voltage VREF1, and an output terminal coupled to the second end of
capacitor C1. Resistor R1 is connected between the node connecting
a drain of P-channel MOS transistor M1 and a drain of N-channel MOS
transistor M2, and the node connecting the inversion input terminal
of differential amplifier G1 and the first end of capacitor C1.
[0051] Differential amplifier G2 has an inversion input terminal
coupled to the output terminal of differential amplifier G1, a
non-inversion input terminal receiving a reference voltage VREF2,
and an output terminal coupled to the non-inversion input terminal
of differential amplifier G1. Resistor R2 is connected between the
node connecting the output terminal of differential amplifier G1
and the second end of capacitor C1, and the node connecting the
inversion input terminal of differential amplifier G2 and the first
end of capacitor C2. Capacitor C2 is connected between the output
terminal of differential amplifier G2 and the node connecting the
inversion input terminal of differential amplifier G2 and resistor
R2.
[0052] Current control circuit 51 outputs and sinks the current in
synchronization with a reference clock REFCLK.
[0053] Current/voltage conversion circuit 52 serving as an
integrator includes capacitor C1 charged and discharged by current
control circuit 51 outputting and sinking the current,
respectively, and generates a triangular wave TRWI based on the
charge stored in capacitor C1 to output the same to comparison
circuit 53.
[0054] Comparison circuit 53 compares the output voltage of
current/voltage conversion circuit 52, that is, triangular wave
TRWI with reference voltage VREF2. Current/voltage conversion
circuit 52 changes the direct current level of triangular wave TRWI
based on the comparison result by comparison circuit 53, and
outputs it as a triangular wave TRWOUT.
[0055] Differential amplifier G2 outputs the voltage showing the
difference between triangular wave TRWI and reference voltage VREF2
to the non-inversion input terminal of differential amplifier G1.
Consequently, the direct current level of output voltage TRWOUT is
fed back to current/voltage conversion circuit 52, with the result
that the operating point of triangular wave generating circuit 102
can be prevented from being displaced over time.
[0056] Furthermore, in order to reduce distortion of triangular
wave TRWOUT, resistor R2 is set to have a resistance value greater
than that of resistor R1.
[0057] Since other configuration and operation are the same as
those of the triangular wave generating circuit according to the
first embodiment, detailed description thereof will not be
repeated.
[0058] Therefore, as in the triangular wave generating circuit
according to the first embodiment of the present invention, the
triangular wave generating circuit according to the second
embodiment of the present invention can prevent the beat noise
occurring due to interference of a system clock and the like, and
thus can prevent the performance deterioration.
[0059] Although the triangular wave generating circuit according to
the second embodiment of the present invention is configured in
such a manner that the output terminal of differential amplifier G2
and the non-inversion input terminal of differential amplifier G1
are directly connected to each other, the configuration is not
limited thereto. The triangular wave generating circuit may be
configured in such a manner that a resistor and the like is
connected between the non-inversion input terminal of differential
amplifier G1 and the node connecting the output terminal of
differential amplifier G2 and the second end of capacitor C2.
[0060] Although the present invention has been described and
illustrated in detail, it is clearly understood that the same is by
way of illustration and example only and is not to be taken by way
of limitation, the scope of the present invention being interpreted
by the terms of the appended claims.
* * * * *